Crohn's disease, an idiopathic inflammatory bowel disease, is characterized by chronic inflammation at various sites in the gastrointestinal tract. While Crohn's disease most commonly affects the distal ileum and colon, it may manifest itself in any part of the gastrointestinal tract from the mouth to the anus and perianal area. Up to the present time, all drugs used in the treatment of Crohn's disease function as prophylactics against the symptoms of Crohn's disease, i.e. inflammation as opposed to being curatives. Established chronic Crohn's disease is characterized by life long exacerbations.
Since its first documentation more than two hundred years ago, the incidence of Crohn's disease has increased markedly and universally throughout the world's populations. The disease is nondiscriminating with respect to sex showing relatively equal incidence of Crohn's disease in both sexes. The anatomic distribution of Crohn's disease has changed in recent years, with an increase in the incidence of large bowel disease. In addition, studies have shown that in the elderly, isolated colonic Crohn's disease is more common than in patients whose disease presents at a younger age, i.e. ages 60 and lower.
The etiology of Crohn's disease is unknown. Immunologic factors have been examined; possible infectious agents have included various enteric bacteria, viruses and chlamydiae. Dietary factors, i.e. fiber-poor diet and stress have also been considered. Mycobacteria is now receiving most focus. The isolation of several different mycobacterial species from Crohn's diseased patients and the knowledge that M. paratuberculosis causes a granulomatous intestinal disease in ruminants has generated keen interest in this organism.
Long standing Crohn's disease predisposes patients to cancer, the most common type being adenocarcinoma which generally occurs in areas where Crohn's disease has been present for many years. Both small bowel and colon cancers occur with increased incidence in Crohn's disease. The increased cancer risk in Crohn's disease is most definitely established for cases of cancer of the ileum, for which the relative risk in Crohn's disease is at least 100-fold greater than in an age/sex matched control population.